While so-called "superconductive" materials have been known for many years, they were impractical as electrical conductors because of the necessity of keeping them at kryogenic temperatures approaching absolute zero. Very recently, however, renewed interest in superconductivity has arisen due to the fact that certain materials, most often alloys or mixtures of more than one substance, have been found that exhibit superconductive properties at much higher temperatures which are well within the realm of practical operating environments, if not for humans, certainly for machines.
Superconductive materials exhibit diamagnetic properties and a diamagnetic material is repelled by a magnet. When such a superconductive material is thus repelled, it is known as exhibiting the so-called "Meissner Effect". A superconductive material, of course, does not exhibit the Meissner Effect at all temperatures, but only at its critical temperature or below. At temperatures above its critical temperature, superconductive materials demonstrate the same properties as the same material or mixture of materials do at normal temperatures.
Accordingly, one sought-after piece of information concerning superconductive material or those suspected of being superconductive is to determine, if possible, the critical temperature at which they become superconductive. Also, when comparing superconductive materials, there is a need for a fast and reliable way of quantifying the superconductivity of two or more different samples, perhaps of the same or, alternatively, of different, materials. There may even be other properties apart from the mixture itself that effect the superconductivity or the lack thereof in certain substances such as, for example, grain size etc., and a reliable way of quantifying or even determining the existence of the Meissner Effect will tell much about these elusive properties.